Trimethyltriazacyclohexane coordination chemistry of simple rare-earth metal salts
Justin C Wedal1, Joseph W Ziller1, William J Evans1
1Department of Chemistry, University of California Irvine, Irvine, CA 92617, USA. wevans@uci.edu.
Abstract:
Reactions of 1,3,5-trimethyl-triazacyclohexane (Me3tach) with common rare-earth metal iodide, chloride, and triflate salts were examined to determine the capacity of this inexpensive chelate to provide alternative precursors for THF-free reactions. The reaction of LaI3(THF)4 and CeI3(THF)4 with 1,3,5-trimethyl-triazacyclohexane in THF generated toluene soluble (Me3tach)2LnI3, 1-Ln, in which the Ln center has a tri-capped trigonal prismatic geometry with two eclipsed Me3tach rings. Reaction with NdI3(THF)3.5 forms the analogous 1-Nd, but a different structure with one outer sphere iodide, [(Me3tach)2NdI2][I], 2-Nd, is also accessible and has a structure reminiscent of bent metallocenes. The reaction of LaCl3 and Me3tach forms the less soluble (Me3tach)2LaCl3, which has a structure analogous to 1-Ln with eclipsed Me3tach rings. The mono-ring yttrium complex, (Me3tach)YCl3(THF)2, could be isolated from the reaction of YCl3 with Me3tach. Reactions of La(OTf)3 with Me3tach were sensitive to the presence of residual proton sources as exemplified by the isolation of {[(Me3tach)La(μ-OH)(μ-OTf)]2(μ-OTf)2}2, 5-La, and [HMe3tach][(Me3tach)2La-(OTf)4], 6-La. SmI2 reacts with Me3tach to produce the Sm(II) complex, (Me3tach)2SmI2(THF), 7-Sm, but 2-Sm can also form in this reaction. Complexes of the larger 1,4,7-trimethyltriazacyclononane (Me3tacn) ligand, namely (Me3tacn)LaI3(THF), (Me3tacn)YCl3, and (Me3tacn)SmI2(THF) were synthesized for comparison. Several examples of the protonated ligands with simple counteranions, [HMe3tach][X] (X = Cl, Br, I) and [HMe3tacn][OTf], were identified in the course of these studies.
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